The FreeBSD Team has issued a security advisory affecting the TCP protocol on current versions of FreeBSD. Please see the message and take measures to keep your FreeBSD system safe and secure by updating with the patches. A detailed report can be found at the link below.

CVE Name:       CVE-2018-6922

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

The Transmission Control Protocol (TCP) of the TCP/IP protocol suite
provides a connection-oriented, reliable, sequence-preserving data
stream service.

To transmit a stream of data, TCP breaks the data stream into segments
for transmission through the Internet, and reassembles the segments at
the receiving side to recreate the data stream.

II.  Problem Description

One of the data structures that holds TCP segments uses an inefficient
algorithm to reassemble the data. This causes the CPU time spent on
segment processing to grow linearly with the number of segments in the
reassembly queue.

Original announcement: https://lists.freebsd.org/pipermail/freebsd-announce/2018-August/001837.html

The Register: FreeBSD has its own TCP-queue-of-death bug, easier to hose than Linux’s SegmentSmack

https://www.theregister.co.uk/2018/08/08/freebsd_tcp_queue_vulnerability/